Porous carbon electrodes with high surface area in the carbon phase are important components in electrochemical devices. Conventional activated carbon electrodes are prepared from activated carbon powder bound by polymer binder. Metallic current collectors are required to shorten the electric pathway between the carbon electrode and current collecting assembly. For use in corrosive liquid electrolyte, the current collector is protected by an electrically conductive coating. Such coating introduces high contact resistance between the coating and the carbon electrode, significant bulk electrical resistance of the coating, and technical challenges for making an uniform thin coating with high electrical conductivity.
Binderless porous carbon composites in electrochemical devices may function as both electrode and current collector. One problem with use of porous carbon composite electrodes is difficulty of attaching a metallic terminal to the carbon electrode. Another problem is relatively low electrical conductivity of carbon compared to metallic or graphitic current collectors. Thus, an assisting current collector bound to porous carbon electrode is often needed. One problem with use of metallic current collectors, particularly in corrosive liquid electrolytes, is the corrosion of the metallic current collector.
In these respects, the disclosed electrode assembly in the present invention by using binderless porous carbon composites as active carbon electrodes departs substantially from the conventional concepts and designs of previous arts. In so doing, the present invention provides flexible and economical ways to assemble porous carbon electrodes with minimum electric resistance.
In the present disclosure, need of an additional conductive coating on the current collector is obviated. Instead the current collector is in direct physical contact with the porous carbon electrode bound by an interfacial polymer binder layer.
Electrochemical devices with multiple cells may require ionic separator as cell separator between the carbon electrodes. In the present disclosure, an interfacial polymer binder layer binding two binderless porous carbon electrodes in direct physical contact functions as an ionic separator.